Field of the Invention
This invention relates to illumination and display technologies, and in particular, it relates to a laser light source, a wavelength conversion light source, a light combining light source, and a projection system.
Description of Related Art
With the advance of semiconductor technologies, the advantages of solid state light sources are more and more evident. Laser light sources, as a high brightness and highly collimated new light source, are being more widely used in projection and illumination fields. Laser light sources have small etendue, and can provide high brightness output light, but also make it more difficult to homogenize the light.
FIG. 1 is a conventional laser light source that uses a square light rod to homogenize the light. Here, elements 11a-11c are laser diodes, elements 12a-12c are collimating lenses, element 13 is a converging lens, and element 14 is a square light rod. The collimating lenses 12a-12c are an array of spherical or aspherical lenses, where each lens corresponds to a laser diode. The laser light emitted by the laser diodes 11a-11c is first collimated by the collimating lenses 12a-12c into parallel light beams, and then converged by the converging lens 13 to a small light spot; the light spot has a size that matches the size of the light entrance port of the square light rod 14. The square light rod 14 is a hollow or solid light transmitting rod, to homogenize the input light beam. However, empirical observation reveals that the light homogenizing effect of this system is not satisfactory, and the light output from the output port of the light rod 14 still has separate laser light spots and does not form a uniform surface distribution. Extending the length of the light rod 14 to increase the number of times of reflections of the laser light inside the light rod does not significantly improve the light uniformity.